I use my tattered old Dell to play an occasional game, including hosting a simple Minecraft server.
It’s a fun game, probably one of the better games made in quite some time because of its open-ended, creative mix of gameplay. I always tell skeptical adults that it’s like “legos for your computer”. My youngsters love to watch me play it, asking me to build or make things, explore caverns, or just try out stuff. Unlike some other games, it really opens imaginative possibilities that many other games and types of games fail to do.
Believe it or not, it is possible to play Minecraft on a G5. You must stick to Minecraft 1.5.1, a much older version than the current release (which is around 1.8.1, I think). Some good people over at the MacRumors forum have even setup a server just for these older G5 users. It looks sweet.
Check out this thread for discussion on the server and directions to finding the right client and launcher to run the thing.
I have not tried this yet, and it seems like it requires a special cracked version of Minecraft, which I certainly don’t have. (And is probably not legal?)
Check out some of the Youtube videos linked in that thread – cute stuff.